The alternate magic system I use is very similar to yours but I rip off the Star Wars D20 force rules (gotta make up for that sticker price somewhere). I also am running a "low magic" game world.
In order to cast the spell, the caster rolls a spellcraft check against a DC of 13 plus twice the effective spell level.
Then the caster resists drain, a will save of 15 plus twice the ESL.
If the caster fails to resist drain the character takes subdual damage of twice the ESL.
I made an excel spreadsheet to alleviate the calculation problems and that seems to calm all the spell caster players.
I was sick of hearing people complain that their casters were ineffective because they didn't prepare the right spell (mages) or they didn't have the spell in the first place (sorcerers). So I got rid of the sorcerer class completely and have wizards cast as often as they like. They get feats that are simply described as "Cast x level arcane spells" when they could normally cast a certain level spell based on the PHB spell progression table.
Effective spell level was my solution to incorporate the metamagic feats and so far it has worked beautifully. simply add 4 to the level of the spell for a quickened spell to get the ESL for example.
The first problem when playtesting this was a caster that could cast healing spells. Why cast cure serious wounds and risk drain when you could instead cast plenty of cure light wounds and have no risk for drain? My solution was that there was one "healing" spell and the casters would cast their best healing spell available every time they cast. It really helps with the "low magic" setting.
Clerics and Druids tend to have a much easier time resisting drain, but their spells are not quite as potent so it works out pretty well.
Then there's the whole force rules rip-off that I used. I basically use Force Points but changed the name to Divine Intervention Points. Players get one per level or one for heroic merit as dictated by the DM. I won't get into the exact mechanics of how force points work because of copyright reasons, but you can basically use the DIPs to give yourself extra d20s on a full round of checks involving d20s. This works great for spellcasters that want to get off a quickened, empowered spell and they're only 7th level caster.
Here's the catch. Those of you who are familiar with SW-RPG remember there's three columns for how many extra d20s you get: Light side, Non- Force, and Dark side. All spellcasters begin as light side users, regardless of initial alignment. IF a caster uses a direct-damage, draining, or destructive spell (ala jedi force use) they receive a dark side point (or taint, as I like to call it). Once you receive enough of these points, your non-destructive spell casting suffers greatly, while your destructive spellcasting improves (not a good trade off mechanically either). Spellcasters always think twice about casting direct damage spells because they will have to make a will save of DC 13+ twice ESL or get a point of taint.
Surprisingly, my players that normally toss fireballs like skittles like this rule. One player that made an invoker likes the rule because it forces him to use his other spells more creatively. It also helps in a role-playing setting because spell casters are regarded more with fear (clerics to a lesser degree of course). Naturally all the players like the DIPs system as well.
And yes, skill focus (spellcraft) and Iron Will are now very popular feats. Unfortunately I don't have my house rules sheets here at work so I could post the numbers with more confidence, but those seem pretty close.
BTW, I also like your ranger class, I have done a similar "Monte Cook" style varient eliminating the spell capability and giving them a couple other feats and class exclusive abilities instead.
